General Discussion
Related: Editorials & Other Articles, Issue Forums, Alliance Forums, Region ForumsI had to put air in my tires when it was 5 below zero last week, the air pressure light came on.
Someone must have let the air out because they were properly inflated when I bought gas 2 days before and my car had been in the garage. I wonder if there is someone going around deflating things. This is very worrisome.
uppityperson
(115,674 posts)dilby
(2,273 posts)we can do it
(12,116 posts)I was able to drive to a gas station normally though, without damage. But they were UNDERINFLATED OMG!!!!1111
global1
(25,166 posts)we can do it
(12,116 posts)maybe it was the gas companies. Quick everyone check your tires!!!!
Blue_Tires
(55,445 posts)and his tire inflation "just happened" to be 11%-13% outside of the regulation norms, then the stewards might want to have a chat...
magical thyme
(14,881 posts)Tire pressure (per square inch) drops between one and two pounds for every 10-degree decrease in temperature, and that can make a big difference to a driver who hasnt filled up since summer.
On a day like today, when the low temperature was 24 degrees, your tires could be 5 to 10 pounds per square inch lower than they were on a 74-degree morning.
So even if you filled up to a comfortable PSI of 32 in August, your tires could have dropped as much as 25 percent by today which in most cars is enough to trigger a warning.
http://www.bostonglobe.com/metro/2014/11/19/cold-you-should-check-your-tire-pressure/eYdwB6XCZsaOGDmd31LBFI/story.html
Blue_Tires
(55,445 posts)which is much more stable in temperature swings than generic 'air' from the local gas station....
jtuck004
(15,882 posts)I mean, what are the odds of that.
we can do it
(12,116 posts)frylock
(34,825 posts)apparently, the Colts had an entirely different weather system on their side of the field.
egduj
(804 posts)That would be weird!
we can do it
(12,116 posts)MANative
(4,105 posts)My mechanic said it was very common. I think "Deflategate" was a natural occurrence.
hifiguy
(33,688 posts)in the winter, I can tell you that in very cold subzero temps the air becomes more dense and takes up less space in the tire - seriously. It's the same reason that if you live next to an airport it sounds like jets are flying ten feet over your house when they take off when it is too frikkin' cold outside: Uncommonly dense air, which acts as a more efficient transmitter of sound.
Weird science!!
we can do it
(12,116 posts)Picked up the car at airport in Billings, drove the Beartooth highway and stayed in Cooke City overnight. Got up early (was like 42 degrees about 35degrees colder than when we got the car) and the tires were nearly flat- drove next door and the gas station lady said it happens all the time)
beam me up scottie
(57,349 posts)I called my brother who was unable to bring me to work because his fuel line was frozen.
Boy that was a sucky day.
FSogol
(45,355 posts)air in ball vs outside air is not great enough to cause deflation. A human deflated the ball.
mythology
(9,527 posts)After all, that must be the reason why the Colts' footballs were still at the legal inflation.
pnwmom
(108,925 posts)Or maybe 50 degrees is just much much colder in Boston than it is anywhere else?
former9thward
(31,798 posts)To answer this question, let's begin with a little equation you may or may not remember from chemistry or physics, back in high school. It's called the Ideal Gas Law:
pV=nRT
where p is pressure, v is volume, n is the number of moles of a gas, R is the Universal Gas constant, and T is temperature.
Remember, what we do to one side of the equation, we have to do to the other side as well. For example, if we increase the pressure (p), then the temperature (T) would have to increase as well. That also means that a change in volume (V) would mean a change in temperature.
We make the following assumptions, based on what we know about the procedure regarding regulation footballs in the NFL and about the Ideal Gas Law:
1) V, the volume of gas (air) in the ball should not change, since (according to procedure), no air is added to or subtracted from the ball after reaching the proper inflation,
2) n will not change for the same reason as above,
3) R does not change, since it is a universal constant.
Now, let's just change the way the equation looks by moving all the letters to one side of the equation:
pV/nRT = 1
From here, we need to think of this as two different times: the pressure, temperature, etc. from when the balls were checked and the pressure, temperature, etc. out on the field. Let's set those to be equal:
p1 V1 / n1 RT1 = p2 V2 / n2 RT2,
where the 1 represents the initial readings and 2 represents the readings on the field. Since the volume will not change (assuming no air is added or taken away from the ball), then V1 = V2, and those can be cancelled. For the same reason, n1 andn 2 can cancel. The R 's cancel, since R
is a constant. We are left with a simple equation:
p1 / T1 = p2 / T2
Now, we can start solving this puzzle quite easily! But before we do, we also have to know the atmospheric pressure during the game, since p in this case is the absolute pressure; the pressure inside the ball plus the pressure of the atmosphere (which exerts a force on the ball as well).
At 6pm, the atmospheric pressure at nearby Norwood Airport was 1009.5 mb (1009.5 hPa or 100950 Pa).
Let's assume that each ball was inflated to the minimum pressure required to meet the NFL rules regarding proper inflation: 12.5 psi. We convert psi (English) to pascals (Metric), which comes out to 86,184.5 Pa and assume a room temperature of 68ºF (20ºC) which converts to 293.15 K (Kelvin, the Metric equivalent). We now have,
(86,184.5 Pa + 100950.0 Pa) / 293.15 K = (p2 + 100950.0 Pa) / T2.
We're down to two variables. But we also know the temperature on the field at the start of the game was reported as 51ºF/10.6ºC (283.15 K). Plug it in...
(86,184.5 Pa + 100950.0 Pa) / 293.15 K = (p2 + 100950.0 Pa) / 283.15 K
Neat! Look, we're left with a solvable equation with one variable, p2, which is the pressure of the air inside the ball at game time! Let's solve this riddle...
Isolate the lone variable:
{[(86,184.5 Pa + 100950.0 Pa) / 293.15 K] * 283.15 K} - 100950.0 Pa = p2
79,800.9 Pa = p2 ---> 11.8 psi
83,244.6 Pa is 11.8 psi, so, according to these calculations, the balls could have been under-inflated by 0.7 psi on the field, just due to the change in temperature from inside to outside. This makes sense given the very first equation, which shows that a decrease in temperature would force a decrease in pressure, assuming the same volume of air in the football.
If we use an indoor temperature of 80º, we would get a final pressure of 11.0 (10.99) psi.
http://www.wcsh6.com/story/weather/2015/01/20/inflate-gate-weather-roll/22065861/
pnwmom
(108,925 posts)The Colts' balls underwent the same weather and testing conditions as the Patriots' balls. And all the Colts balls tested within regulation limits.
(And why would anyone use an indoor temperature of 80 instead of 70?)
NutmegYankee
(16,177 posts)A motorized pump usually heats the air from compression. The Colts may have inflated their balls towards the high end of the scale and used manual pumps while the Pats used a motorized pump and left the balls at the low end.
pnwmom
(108,925 posts)And the league tested all the balls before they went into the game. Why hasn't the league simply announced that the Colts' balls started out significantly heavier than the Patriots' balls? Instead of letting all this furor go on?
NutmegYankee
(16,177 posts)The only one throwing the ball is him. Some actually prefer them even harder than regulation. They tailor it for their taste and have the receivers train to catch them.
In reality, 10.5 and 12.5 isn't a huge difference. You have to have a damn good handgrip to notice, which is why the refs probably never did.
pnwmom
(108,925 posts)on their hands to judge.
If this problem were simply explained away, as you have tried to do, the League would have done this by now. Instead it's standing back while everyone says, "Ask the other guy. It's not me!"
NutmegYankee
(16,177 posts)If the air is warmer than room temp in the ball at test time, insulated by a bladder and skin that don't transfer heat well, the pressure will be within spec at test time - which is all that matters. Later, the air comes to equilibrium with the much cooler outside air over two hours, and is now low. HAPPENS EVERY GAME.
pnwmom
(108,925 posts)and were tested under the same conditions.
And yet, magically (or not), only one set of balls turned out to be at least 2 pounds underweight, in 11 out of 12 cases.
Sorry, but physics doesn't explain that.
NutmegYankee
(16,177 posts)I guess you see physics as magic.
And yes, I understand physics quite well - I'm a professional Mechanical Engineer who works on compressed gas systems.
pnwmom
(108,925 posts)your explanation as the correct one.
You think they wouldn't tell us if the teams used different methods for inflating their balls? Right. Under all this pressure, they're not offering us that simple explanation.
Because it isn't true.
NutmegYankee
(16,177 posts)And the haters hate, like usual.
pnwmom
(108,925 posts)hang out for days, letting this whole scandal suck the air out of the Super Bowl, when -- according to you -- they could have just explained all this away a long time ago.
Not likely.
NutmegYankee
(16,177 posts)Like they have a clue.
former9thward
(31,798 posts)Were the Colts balls and the Pats balls in the same place when measured. I don't know.
pnwmom
(108,925 posts)explained it, why aren't they and the League speaking out?
If there was an innocent explanation don't you think they'd have figured it out by now?
former9thward
(31,798 posts)I really don't get the NFL investigation. Brady said yesterday they had not spoke to him. I would think he would be the first person they talked to.
pnwmom
(108,925 posts)And this is the 5th day now.
former9thward
(31,798 posts)ball runners, QB, and coach in a days time. It is not that hard and Goodell has the power to do that. Maybe they want to push it back to after the Super Bowl. I don't know.
jberryhill
(62,444 posts)"Since the volume will not change (assuming no air is added or taken away from the ball)..."
The volume of an elastic container is a function of the pressure. It is not a constant for this model.
NutmegYankee
(16,177 posts)jberryhill
(62,444 posts)It is the entire point of deflating them for better grip.
MohRokTah
(15,429 posts)In the deflated balls cheat by the Patriots.
Weird that, eh?
madokie
(51,076 posts)If I had a foot ball I'd make a check just to satisfy myself on this.
pnwmom
(108,925 posts)Because science would tell us that the Colts' balls experienced the same temperature and testing conditions as the Patriots balls, and therefore the effect should have been the same on all the balls. But only the Patriots' balls tested underweight.
madokie
(51,076 posts)I say its our neighbors who do that to us
from a room temperature ball to a sideline ball there would definitely be a difference in the pressure
pinboy3niner
(53,339 posts)doc03
(35,143 posts)a couple months ago when the weather was warmer. The tires on the truck read between 26.5 to 27.5 pounds. I brought them all up to 30 pounds and the TPM light was still on. I checked the spare and it was at 24.5 pounds, I remembered I hadn't check it since in the summer when it was in the 80s. Air pressure can vary several pounds with temperature. I hear if you inflate your tires with nitrogen you don't have that problem. Maybe they could use nitrogen in footballs.
NutmegYankee
(16,177 posts)And oxygen reacts very much the same. At least, at the temps we normally encounter.
doc03
(35,143 posts)no water vapor in it. We used nitrogen in our pneumatic impulse lines in the steel mill because we couldn't chance having the lines freeze up in cold weather.
NutmegYankee
(16,177 posts)It just requires a dehydrator system. We use them in my industry for our compressed air. But I'm sure a nitrogen like MIL-PRF-27401 Type I Grade B and C would do the trick for freezing.
doc03
(35,143 posts)in the lines. Had lots of problems in the winter.
Omaha Steve
(99,054 posts)They did Nitrogen in the tires for free. There is a difference.
Some believe it helps with tire fires too.
NutmegYankee
(16,177 posts)The only reason I think you see a difference when they use nitrogen is they use pure nitrogen, while the air is whatever is outside (humidity and all) simply compressed. If you used CGA grade scuba air, I'd expect a similar result.
I use nitrogen when testing 100% oxygen systems because it acts like oxygen, but isn't a fire hazard if it's leaking.
Major Nikon
(36,814 posts)But I'm not so sure they would be cheaper. Compressed nitrogen is very cheap to produce and transport.
Major Nikon
(36,814 posts)...for a good reason.
As someone pointed out, it's not so much the difference in gases, but rather the difference in water vapor.
Capt. Obvious
(9,002 posts)and someone that was banned should be allowed to take your place.